Themes > Science > Earth Sciences > Geology > Soils > Soil Morphology > Soil Morphology > Special Features

Special features occur is soils which should be recorded additionally. Ped exteriors include clay coats, organic matter coats, silt coats, sand coats, carbonate coats, manganese coats, slickensides, stress surfaces, and clay bridges between sand grains. Ped interiors include concentrations of oxides, nodules, soft accumulations, pseudo-rock fragements, plinthite, and streaks. In particular, concretions are resulting from alternate periods of reducing and oxidizing regimes. Another special feature might be the evidence of animal activity by burrowing animals or high eaethworm acitivty. 

Concentrations

Def: Soil features that form by accumulation of material during pedogenesis. Processes involved: Chemical dissolution/precipitation, oxidation and reduction, physical and/or biological removal, transport, and accumulation

Types:

Finely disseminated materials:

Small precipitates (e.g. salts, carbonates) dispersed throughout the matrix of a horizon

Concentrations

Masses:

Noncemented bodies of accumulation of various shapes that cannot be removed as discrete units (e.g. crystalline salts)

Nodules:

Cemented bodies of various shapes that can be removed as discrete units from soil

Concretions:

Cemented bodies similar to nodules, except for the presence of visible, concentric layers of material around a point, line, or plane

Crystals:

Macro-crystalls forms of relatively soluble salts (e.g. gypsum, carbonates) that form in situ by precipitation from soil solution

Biological concentrations:

Discrete bodies accumulated by a biological process (e.g., fecal pellets, insect casts)

 

Ped & Void Surface Features

These features are coats/films or stress features formed by translocation and deposition, or shrink-swell processes on or along surfaces. They are described in terms of kind, amount, continuity, distinctness, location, and color.

 Examples:

Ferriargillans (Fe 3+ stained clay films)

Mangans (black, thin films of Mn)


Information provided by: http://www.soils.wisc.edu